But I did the same thing yesterday with just web browsing & no other programs running & after few minutes that fan was running like crazy.
This screams component temperature problem.
I'd recommend NOT using web browsing as a test since that can be a highly variable load. Normally web browsing is a low stress task, but maybe you're visiting sites that are running background scripts to mine cryptocurrency from your PC while you're on their site.
Certainly passively cooled GPUs can get hot, but since this situation just recently started happening, it's unlikely that ALL of the GPUs' heatsinks came loose at the same time, but it probably only takes one steamy GPU to trigger the fan speed increase. 58C isn't high at all, but it sounds like that was the temp during your successful test where the fan didn't scream. It would be interesting to know what the GPU temp(s) are when the machine pushes the fan speed up.
Main: i5-3570K, ASRock Z77 Pro4-M, MSI RX480 8G, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod